PARTIAL DEFECT TESTER: A NOVEL APPROACH TO DETECT PARTIAL DEFECTS IN PRESSURIZED WATER REACTOR SPENT FUEL

摘要

A novel methodology to detect diversion of spent fuel from pressurized water reactors (PWRs) has been developed in order to address a long unsolved safeguards verification problem for an international safeguards organization such as the International Atomic Energy Agency (IAEA) or European Atomic Energy Community (EUR-ATOM). The concept involves inserting tiny neutron and gamma detectors into the guide tubes of a spent fuel assembly (SEA) and measuring the signals. The guide tubes form a quadrant symmetric pattern in the various PWR fuel product lines, and the neutron and gamma signals from these various locations are processed to obtain a unique signature for an undisturbed SEA. Signatures based on the neutron and gamma signals individually or in a combination can be developed. Removal of fuel pins from the SEA will cause the signatures to be visibly perturbed thus enabling the detection of diver- sion. All of the required signal processing to obtain signatures can be performed on standard laptop computers. Monte Carlo simulation studies and a set of controlled experiments with actual commercial PWR SFAs were performed, and they validated this novel methodology. Based on the simulation studies and benchmarking measurements, the methodology promises to be a powerful and practical way to detect partial defects that constitute 10% or more of the total active fuel pins. This far exceeds the IAEA goal that for SFAs that can be dismantled at the facility-which is essentially the case for most PWR fuel-the partial defect test used should assure that at least half the fuel pins are present in each SEA. The methodology does not rely on any operator-provided data like burnup or cooling time and does not require movement of the SEA from the storage rack in the spent-fuel pool.